laser

### Laser Probe Toolbox: CWS Parameter tab

Probe Toolbox - CWS Parameter tab

The CWS Parameter tab in the Probe Toolbox is available once the system has been appropriately configured:

- The CWS has to be configured as the active laser system. Usually, this is done locally by the factory during the startup procedure or by a Service Engineer.

- Once the system is correctly configured, you must define a probe with the correct properties. The probe is constructed through the Probe Utilities dialog box. You should use the OPTIVE_FIXED selection and a lens that includes CWS. This should be defined in the USRPROBE.DAT file. This is also usually provided locally by the factory.

The columns in the tab can include the following information:

+ TOLERANCE

Defines the upper tolerance value for the measurement.

- TOLERANCE

Defines the lower tolerance value for the measurement.

SENSOR FREQUENCY (Measurement Rate)

The measurement rate sets the number of measured values that the optical sensor records per unit of time. For example, when the measurement rate is set at 2000 Hz, 2000 measurement values are taken per second. The intensity indicator on the display can help you select the correct setting.

Setting Range

As a rule, you should strive to measure at the highest possible measurement rate in order to acquire as many measurement values in as little time as possible. In the case of surfaces with very low reflectivity, it may be necessary to reduce the measurement rate. This has the effect of illuminating the optical sensor‘s CCD-line longer and thus makes it possible to perform measurements, even if the reflected intensity is very low.

Overmodulation of the CCD-line on highly reflective surfaces and at small measurement rates can lead to measurement errors. If the intensity indicator displays a blinking ,,Int: 999", overmodulation is occurring. When overmodulation occurs, the next-highest measurement rate should be selected. If the maximum measurement rate (2000 Hz on CHRocodileS, 1000Hz on CHR150E) is already set, the reflected intensity can be reduced in one of two ways:

- By positioning the sensing head in the upper or lower threshold of the measurement range

- By engaging the autoadaptfunction (where the AUTO LAMP parameter is set to YES). This will adapt the lamp intensity continuously depending on the part reflection. Here, a dark reference is not used. This is the method supported in PC-DMIS.

AUTO LAMP (Adjust Lamp Intensity)

Under adjust lamp intensity, the relative pulse duration of the LED and with it the effective brightness of the light source can be selected.

If a highly-reflective surface is being measured, on which the highest measurement rate still results in overmodulation, then it makes sense to reduce the exposure time.

If a poorly-reflecting surface is to be measured with a high measurement rate, this can be achieved by means of a longer pulse duration.

AUTO LAMP: NO

When the function is turned off, the current light intensity of the LED is used.

AUTO LAMP: YES

The independent adjustment of flash time for the LED during an exposure time makes it easier for you to automatically receive the best intensity settings when measuring on variable surfaces and with it an optimal signal-to-noise-ratio.

The brightness of the lamp is modulated such that a defined percentage of the modulation amplitude is achieved. The value can lie in the range of 0% to 75%. For most applications, a brightness value between 20% and 40% is recommended.

EXPOSURE TIME (Brightness Value)

If the AUTO LAMP parameter is set to YES, the exposure time (brightness value) can be selected here.

The brightness of the lamp is modulated such that a defined percentage of the modulation amplitude is achieved. The value can lie in the range of 0% to 75%. For most applications, a brightness value between 20% and 40% is recommended.

FILTER [SENSOR INTENSITY] (Detect Threshold)

Under Set Detect Threshold, the value for the threshold between noise and the measurement signal can be set. Peaks falling beneath this threshold are recognized as invalid and show on the display as the measurement value "0".

For a valid measurement, the intensity should fall between 0 and 999 on CHRocodileS or 99 on CHR150E; otherwise, the measurement rate must be changed.

If the distance to a surface with low reflectivity is measured, the intensity of the reflected light can be too low, and the measurement rate must be reduced. For a measurement rate under 1 kHz, a threshold of 40 on CHRocodileS or 25 on CHR150E is recommended. This prevents measurement values of too low an intensity, which rise only slightly above the noise, which would falsify the measurement.

At a measurement rate of 1 kHz and higher (only for CHRocodileS), a threshold of 15 is expedient in fully exploiting the device’s dynamics.

OFFSET

This is the offset the machine will move in the measurement direction in addition to the measurement position.